High-voltage circuit breaker



July 21, 1953 J. D. woon ETAL HIGH-VOLTAGE CIRCUIT BREAKER 4 Sheets-sheet 1 Original. Filed Jan. 11,. 1947 Attorneys July 21, '1"95'3v 1 D, woon '2,646,482

' HIGH-,VOLTAGE `cIRgCuWIT BREAKER?,

original Filed Jan 11, 1947 4 snetssheet s.

1NVENToR5 Atto P we) s osepb D. Wood By ArJibuPCaswell Ohm Patented July 21,1953

HIGH-VOLTAGE CIRCUIT BREAKER Joseph D. Wood, Upper Darby, and Arthur S'. Caswell, Philadelphia, Pa., assignors to I. T. E. Circuit Breaker Company, Philadelphia,.Pa., a corporation of Pennsylvania Original application January 11, 1947, Serial N0.

721,648, now Patent No. 2,613,299, dated October 7, 1952. Divided and this application June 4,1947, Serial No. 752,426

v12 claims. (Cl. 20o-147) 1 Our present invention which isa division of United States application Serial No. 721,648, filed January 1l, 1947, now Patent 2,613,299, October 7, 1952, relates to high voltage high capacity circuit breakers, and more particularly to circuit breakers having an interrupting rating of 50,000 kva. and better in any voltage range between 2300 and rk5000 volts,v and'at current ratings of 600 and 1200 ramperes.

In a high voltage high capacity breaker the first and most important step involved is the construction of the arc chute and of the arc blowout mechanism so that any arc which is drawn between the contacts asthey open may be readily extinguished before damage to the breaker or to the circuit may occur. 5

Our novel circuit breaker includes a simple unitary arc chute structure madeas a single unit provided with a disconnect and so arranged that it may readily be mounted on the circuit breaker and connected thereto or removed therefrom as `a whole without the necessity for special tools.

the contacts of the circuit breaker or for replacement or repair of any part that may require such replacement or repair. .L

Many cbjects of our invention will become-ape parent from the following description of the drawings in which 'l i Figure 1 is an enlargedr side front view in perspective partially broken away showing the lowerv terminal assembly, upper terminal assembly, the blow-out coil assembly and the movable contact bridge assembly. .y 'n

Figure 2 is a side view of the arc chute assembly.

Figure 3 isa front view of the arc chute assenti-.- bly.

` Figure 4 is a top view of the arc chute assembly. Figure 5 is a side view of the interphase barrier.

Figure 6 is a iront view of the interphase barrier.

Figure 7 is'V a perspective and partially exploded e view oi a `portion of the arc chute of' our novel circuitl breaker.

The specic novel assemblies or sub-assemblies forming an essential 'Y part of the novel circuit breaker here shown are the operating mechanism shown in Figure 3 of the parent application Serial '-1 to provide a solenoid closing means.

2 No. 721,648, filed January 11, 1947, now Patent 2,613,299, October 7,1952, the lower terminal assembly shown in Figure 1, the upper terminal assembly of Figure 1, the movable contact arm or bridge assembly of Figure l, the blow out assembly of Figure 1, the arc chute assembly of Figures 2, B and 4. The specic operationr of these individualr assemblies renders possible the entire high speed high capacity circuit breaker which our novel unit embodies. Additional assemblies which facilitate the operation are specifically described in connection with Figures 5 and 6 which show the interphase barrier assembly and Figures 10, ll and 12 of the parent application Serial No. 721,648, led January 1l, 1947, now Patent 2,613,299, October 7, 1952, which show the rack and indicator assembly.

The various assemblies above mentioned will be described in'order, going from the bottom toward the top of the circuit breaker without specific emphasis on any one'of `the assemblies over the other. n

It must be emphasized, however, thatran important feature of the circuit breaker is in the novel arc chute construction in conjunction with the novel blow out construction.

The operating mechanism utilizes as closely as possible the simple principle of the lever operated switch with only enough addition thereto to provide automatic response to overcurrent conditions in order totrip the circuit breaker and also The simplication of this operating mechanism makes possible the production of the inexpensive circuit breaker herein described. f

Thus, while .the arc chute assembly and the blow-out assembly make possible the high capacity operation and high speed operation which are essential to the operation of the circuit breaker as aV whole, the simplicity of the other assemblies makes possible the economical and eflicientv construction.

Thel upper terminal assembly 30, and the lower terminal assembly 3| for each of the three poles is formed from a single bar of copper of rectangular cross section appropriately insulated by phenolic insulation as described more speciically hereinafter in connection with Figure 1. The terminal assembly elements 30, 3| are carried* by the vertical supports l0 and Il, as

'January 11, 1947, now Patent 2,613,299, October 7, 1952. Each of the vertical members I0, Il and 32 is recessed at 33, 33 to receive the terminal members and accurately position the same. Each of the terminal members is provided with a side plate or flange 35 hereinafter more specically described in connection with Figure 2 of parent application Serial No. 721,648, nled January 11, 1947, now Patent 2,613,299, October 7, 1952. Each of the vertical reinforcements ill, il and 32 is a rectangular steel member, so that while the recesses 33, 33 are cut out in the vertical reinforcement they are incised only in the portion of the rectangular steel member which is normal to the back panel 56. The legs of each of the rectangular members i9, ll and 32 carry the bolts 35, 36 which engage the flange members 35 of the terminal element. Thus it will be seen that two bolts or screws 35 are all that are necessary to secure each of the terminal elements in place, these bolts being locked in secured position by the nut 3l' as shown in Figure 2 of parent application Serial No. 721,546, filed January 11, 1947, now Patent 2,613,299, October 7, 1952.

Each of the upper and lower terminal assembly members 39 and 3l also carry the spring biased disconnect contact elements 3S, 35 shown also in Patent Number 2,029,028. The intermediate cross bar I3, which is secured to the vertical members I9, Il and 32 by the bolts 56, also carries at its outer end the wheels 42 on an appropriate shaft extension thereof, the said wheels 42 cooperating with appropriate tracks in the compartment to guide the truck into and out of the compartment properly.

The movable contact assembly shown generally at 59 cf Figure 1 is connected at its lower end to the lower terminal assembly 3 in the manner hereinafter described, and is provided with a link which is connected to the contact operating arms 52 projecting up from the operating mechanism assembly 45. The mot/'able Contact bridge assembly which of course has as many poles as there are upper and lower terminal assemblies, three in the particular instance shown, is provided with contact elements hereinafter more particularly described in connection with Figure 1. The blow out coil assembly 53 which includes the coil 54 of Figure 1 and the laminated blow out iron legs 55, is mounted on the upper insulating back panel also across the bars 5 and i4 and the upper portion of Vertical supporting members IG and Il and is supported thereby.

Itis spaced from the bars I5, Ii, 32, ifi, i5 by the upper insulating baci: panel 55 which panel is secured across the bars l5, i l and 32 as shown in Figure 1. Appropriate openings 59, 59, are provided in the panel 55 to permit the terminal members 3@ and 3l to project therethrough in a manner shown in Figure 1.

The arc chute assembly 57 is supported by the blow out assembly 53 and particularly by the laminated legs 55 of the blow out iron which ride between the bracing bars 56, 5B on each side of the arc chute as shown in Figure 2, and as will be more specically described hereinafter in connection with Figures 1 and 2.

As will also be hereinafter pointed out the front' arc runner 253i (Figure 25 of the parent application Serial No. 721,648, filed January 11, 1947, now Patent 2,613,299, October 7, 1952) of the arc chute is not connected in any way to any of the other elements of the circuit breaker but is brought into the circuit by the proximity of the moving Contact 20A thereto during the opening operation. The rear runner 290 (Figure of the parent application Serial No. 721,648, led January 1l, 1947, now Patent 2,613,299, October 7, 1952) of the arc chute 51 is connected to the circuit breaker through the blow out coil mechanism 53 by the clip arrangement indicated generally at 392- of Figure 1, and also hereinafter more specically described. The arc chute is entirely supported by the laminated legs of the blow out iron on each side, being retained in position by the latch assembly GI (Figure 2) also hereinafter more specifically described.

The nal unit assembly comprises the interphase barrier assembly indicated generally at 63 of Figures 5 and 6. The interphase barrier being supported at the rear end by resting on the cross bar 65 (Figure 2 of the parent application Serial No. 721,648, led January 11, 1947, now Patent 2,613,299, October 7, 1952) secured across the lower end of the panel 5G and by restat the front end on the angle iron 66 carried by the racking and indicator assembly 43.

Blow out assembly The blow-out assembly 53 comprising the coil 54 and the laminated blow-out iron legs 55 is shown in Figure 1. The coil 54 is connected by the lead 235 and bolt 236 (Figure 1) to the upper terminal bar i60. The opposite end of coil 54 is connected by lead 238 to extension Illa on contact bar |71 passing through a slot in the upper extension llOa of insulating strip (Figure 1). Coil 54 is wound on an iron core 249 to which is secured the laminated blowout iron legs 55 on either side.

We have found that preferably four such side plates on each side 1/8 thick ensures a proper distribution of magnetic blow-out flux over the full length of the side plates. Also we have found that in order to obtain a proper blow-out flux without inserting too much impedance in series with the arc it is desirable that the coil 54 consist of 118 turns of copper strips of 1%; x

The side frame members 242, 242 (Figure 1) of the blow-out assembly are secured against the core 24D by bolts 243 which also secure the plates 55 against the core. The side frame members 242 of the blow-out assembly have secured therebetween the upper block 245 by means of pin 245 and the lower block (not shown) by means of pin 248 and plate 249 by means of screws 250.

Blocks 245 and its corresponding lower block are provided with tapped openings by means of which the entire blow-out assembly may be readily secured to the frame of the circuit breaker. It will thus be seen that the entire blowout assembly may be readily mounted on and removed from the circuit breaker as a single unit.

Arc chute The blow-out assembly serves as support for the arc chute described in Figures 1, 2, 3, and 4. The arc chute assembly 57 mounted above the contact assembly 8G provides for a positive and eilicient arc interruption. It consists of insulation side walls 257 (Figures 2-5), front and back arc runners 29l and 290, respectively, and a series of ceramic plates 260 (Figure 7) mounted in spaced relation transverse of the arc path and a strong magnetic blow-out eld to force the arc into the arc chute.

The sides 257 (Figures 2 and 4) have fastened at their lower portion, adjacent the arcing area,

inner arc resisting insulating plates 269-269 5 of special composition hereinafter described. The arc resisting plates 269 are chamfered along their upper edges at 262--262 to provide a straight locking edge for the cross plates 260 and the spacers 26|. The lower ends of the cross plates 290 and the spacers 26| are appropriately shaped to t the chamfered edge 262.-

As the arc is driven into the chute by the magnetic field, it passes rapidly through the arc extinguishing ceramic plates 260 which are rectangular inshape at the top and have a long tapered lower edge extending from the center of one side of the plate to the lower corner on the opposite side of the plate. A ceramic rspacer 26| is provided to support each plate and position it with respect to adjacent plates and forms with the long tapered surface of the plate, a triangular opening with the apex at the top for the passage of the arc. Each plate with its spacer presents'a decreasing area for the arc as it rises and gradually squeezes it into a narrow slot 301.

The plates 260 are assembled alternately in an interleaved relation and spaced from each other so that the long tapered surfaces cross at the center of thev chute directly above the path of the arc as it travels up the chute. As the arc passes the crossover point of the plates it is forced into a zigzag or sinuous path gradually but rapidly increasing its length and bringing it into contact with larger and larger cool surfaces of the plates. The arc must thus bend around the edges of the plates which are effective in circuit interruption. The positive and efficient arc interruption is affected by the cooling, lengthening and squeezing of the arc at numerous points all along its path.

Provision for the interruption of low current arcs is built into the arc chute. No moving parts or auxiliary equipment are necessary. Short circuit or normal overcurrents are extinguished before the moving arc horn 201 passes the front arc runner 29|, The arc formed by currents of low value is extended in the chute beyond the front arc runner 29| and effectively -cooled and deionized by a set of plates 322 (Figure 3) located in the current path.

Arc travel toward the front of the chute involves a transfer from the arc contact arm 201 to the forward arc runner 29|. The absence of the return connection from this runner to the lower lead is a new feature in -high voltage breaker design. Without this connection the dielectric strength of the open breaker is not dependent upon the arc chute, whose inner surfaces are bound to deteriorate through use. Without this connection, the arc between the contact arm 204 and runner 29| continues as long as the arc exists. On high values of current the arc is extinguished before the arc contact arm 204 passes the runner 29|.

Progress of the arc up into the chute brings it in contact with the cross plates 260 which are shaped and assembled so as to cause the arc to follow a gradually increasing zigzag farm, thereby securing a long arc length in a short length of chute. Maximum length in a crosswise direction is realized at a point opposite with the top of the blowout iron side plates 55 -where it enters a narrow confining slot 301. of the plates 260 above this point is used to cool and deionize the incandescent gases which result.

When the current to be interrupted is of low value, low magnetic action existing atv that time The length 5 is still sufficient. The arc is extended by the long travel of the arcing tips and cooled by the specially located plates 322 below the front arcing horn 29|.

The plates 260 are held in position in the arc chute by the insulating cross-bar 263 (Fig-l ures 2-4) carried in the slot 264 ofthe end pieces 261. Insulating cross-bar 263 is securely y fastened by bolts 265, 266, respectively,'at the front and back end pieces 261 of the arc chute assembly 51 which extend up above the side plates 251.

The side plates 251 are connected together at the front'and back end of the arc chute by bolts 268 which connect them to the front and back strips 261. The side plates are provided withinsulating bracing bars 58 secured thereto by the bolts 268 and spaced apart by the Width of the laminated blow-out iron legs 55.

The materials used in the construction of the arc chute play an extremely important part in the performance Vof thecircuit breaker.

The side plates 251 are made of Bakelite With a layer of fibre on each side. During interruption not only full voltage is applied to these plates but frequently switching surges of very high value are encountered. The high insulating value of' Bakelite is desired, but it alone would not be satisfactory since it has the characteristic of carbonizing and tracking if any arc orhigh temperature arc gases come in contact Vwith it. Consequently, the Bakelite is coated with nbre which does not have 'this characteristic. Furthermore, an arc resisting insulating varnish is applied to the fibre to keep it from absorbing moisture. Furthermore, the spacers 26| for the cross-plates 260 completely line the inside of the arc chute in the lower part where the arc is drawn and prevents the arc coming in contact with the side 'plates at any point.

The material of which the cross plates 260 and the spacers 26| are made, determines to a large extent the ability of the breaker to interrupt currents. The least expensive material that is at all suitable for this application is the asbestos cement board called Transite. 'I'his material gives fair operation and for low interrupting capacities is quite suitable. In aneffort to increase the interrupting capacity, numerous materials were tried. Gas forming materials such as fibre were found to be unsatisfactory as they increased the display incident to circuit interruptions andthe excess gas had a tendency to initiate arcing in other parts of the breaker. InertY materials were better. Porcelain, while quite good was too fragile and could not be manufactured in thin plates with sufficient accuracy to make it practical.

By far the best material found was the glass bonded mica consisting of mica dust and glass fused and pressed at high temperature and pressure. It is inert at the temperatures encountered in the arc chute, an excellent insulator, does not absorb moisture and is a non-gas forming material. This material when used for the arc plate and spacers increased the interrupting ca pacity to more than twice the value shown by other materials. plates 250 and spacers 25| but also for the arc resisting plates 269 that come in contact with the arc.

The arc chute may be mounted in position by being slid on to the laminated blow-out iron legs 5K5 so that the reinforcing bars 58, 58 act as run- It is used not only for the cross ners to receive the laminated legs 55, thus hold-y ing the arc chute in position.

In order to ensure a further distribution of magnetic blow-out ilux down into the region of the contacts, an additional iron plate 213 is provided on each side of the arc chute secured to the bracing bars 38 by screws 2li and having eX- tension 2l2 extending down into the region of the contacts outside the plates 5i.

The blow-out flux through the laminated blowil out iron legs 55 is also communicated to plate 2li) and by extension 212 is communicated down into the region of the contacts to increase the blow-out effect in that region. The runners or bracing bars 53 on one side of the arc chute are provided with the bronze springs 28D connected as shown in Figure 2 between the runners or bracing bars 58 by screws 28i and a. latch assembly 6| secured thereto in any suitable manner as by thescrews 233, 2&3 (Figures 2 and 3) and having a projection 232 which engages a corresponding detent 231i inthe laminated iron leg 55. Thus thearc chute is supported by the laminated legs 55 between runners 58 on each side and is latched in position by the latch assembly 3i engaging detent 23@ in laminatedlegs 55. To remove the arc chute it is only necessary to press in the latch assembly 3l to disengage the detent 284 from laminated iron legs 55 so that the arc chute may be slid out. As already stated, the arc chute is provided with a back arc runner 233 and a front arc runner 29l converging below the arc chute and toward the center in the region of the contacts, the front arc runner 291 having extension 291C toward the contact and the rear arc run- 1:

ner 29S having extension 296A toward the contacts and the further rearward extension 233.

rlhe portion IHA (Figure l) of the upper terminal to which lead 233 of the blow-out coil is connected is :also provided with the spring clip 300 (Figure 1) to receive the rearward extension 293 of the rear arc horn 29B of the arc chute 5l. Thus no special connection need be made for the arc chute; but when the arc chute is slid into position, the rear extension 293 of the rear arc horn r2.3i) moves into the spring clip and the rear arc horn is thus connected to the end 238 of blow-out coil 511.

The section 290B of the rear arc horn rests on plate lli to obtain further contact to the rear arc horn 29D. Thus when the section of the arc on the stationary arcing contact jumps to section 293A of the rear arc horn, the current path isA from terminal 33, bolt 238 to lead 235 to coil 54 to lead 233 to sectioni1lA cimember ill and spring clip 333. to section 290B of rear arc horn 233. Then through the arc chute to the movable arcing contact and then to the front arc runner 23! as hereinafter more specifically described.

The cross plates 260 as shown particularly in Figure 3 are each of an insulating non-Carboniaing material, preferably a glass bonded, mica ceramic material or of a material known as Transite. These plates are longitudinal members as shown in Figures 3 and 4 having a curve at section 333 of a very large radius; upward of this position they have a curve 304 of smaller radius; and above that position have an extension 365 entering the notch 26D and closing oir that side of the plate.

The side of each plate opposite the curve is ilat. When the arc is iirst drawn it is driven up by the blow-out mechanism into the notch 3H) of V-shaped cross-section formed by the curves Then from spring clip 386 303-384 of the alternately arranged plates. As the arc is driven up further beyond the apex of the notch, it is caused to zigzag laterally in ilowing past the curves 33!!- of the alternately arranged plates. It thus passes through the relatively narrow notch 351i on one side of one plate and then through a similar relatively very narrow notch on the opposite side of the alternate plate and back and forthA laterally through the arc chute.

If the arc is not extinguished. when the arc has reached this point, the magnetic blow-out blows the larc up still further past extension where in addition to the lateral zigzagging and lengthening of the arc, the arc is zigzagged vertically. This combination of extreme lateral zigzagging with vertical Zigzagging of the arc ensures extinffuishment of the arc before the top of the arc chute is reached. rThe combination of 'lateral zigzagging with vertical zigzagging limits the upward travel of the arc.

Thus, it will be seen that one of the essential elements of the arc chute herein described is first the lateral zigzagging or lengthening oi the arc as it is blown up into alternating thin narrow slots oneach side. Thereafter the portion of the arc between the cross-plates Z is free to move up to superimpose on the lateral zigzagging or lengthening of the arc, a vertical zigzagging or lengthening.

Also it will be seen that there is no connection whatever' between the front arc horn 29! and the lower terminal or any other terminal when the circuit breaker is closed or open.

Interphase barriers The interphase barrier assembly E3 is a complete structure shown in Figures 5 and 6 sui iiciently light to be easily handled by one man. Preferably it is installed as a complete unit, but if the oven storage space is at a premium, the interphase barrier may readily be stored knocked down to be assembled by driving a number of screws through registering openings,

rEhe interphase barrier assembly as shown in Figures 5 and 6 comprise a pair of side plates 33!) connected together by the front plate 332. Corner pieces 335, 3.35 are provided at each side to receive the screws 335, 336 of the front plate 332 and the screws 33?, 337 o1" the side plates 33B.

Further reinforcing strips 3130 are secured to the iront panel 332 by screws Sill to provide a means of securement and spacing for theinterphase barriers 325. An additional notched top strip 359 is secured to the iront panel 332 at the upper end, the notches therein providing spacing elements for the interphase barriers. The rear ci the interphase barrier may have cross bars 352, 352 secured thereacross by screws 353 entering into the opposite outside panels 333. These cross bars may also be notched to receive and position the interphase barrier elements.

Each hole or space in the interphase barrier may have secured therein between appropriate reinforcing blocks 3F18 the horizontal barrier 36! to prevent ionized and heated gases from being blown down in the arc chute.

In Figures 1U, ll and l2 of the parent application Serial No. 72l,648, filed January 11, 1947, now Patent 2,613,299, October '7, 1952, we have shown the racking and indicator assembly, which is carried by the operating mechanism assembly 4G. The arm itil carries at its outer ends the rollers 44, dit which roll upon the track of the cubicle or compartment. Latches in the cubicle hold the arm 433 and lock it in position.

When the racking crank is inserted through pening' 402 in the front plate 403 into the socket 404 of the racking screw 405 and turned, the relative positions of the frame 405 comprising the side elements 401, 401 and the arm t0 are changed. Since the frame 406 isfastened to the front wall of the mechanism 46 and the arm 400 is held in a xedposition within the cubicle by latches (not shown), the rotation of screw 405 moves the breaker from test to operating position.

This is so because the screw 405 passes through a threaded opening 4|0 in arm 40D and is rotatably carried in the bearing 4| of the rear frame element 4|2 of the frame 406. A shutter 420 prevents the insertion of the crank through opening 402 into the racking screw 405 whenever the breaker is closed. Theindicator 430 is operated by link 42| which is connected at oneend to the bell crank arm 43| of the indicator 43s, and at the other end to the pin |09 in the Contact operating arms 52. When the breaker is closed .by either the solenoid closing mechanism 49 or the manual closing arm |30, the contact operating arms 52 are rotated counter-clockwise (with respect to Figure l) and thereby draws the link 42| back to actuate the counter 44| and the indicator 430. When the indicator dell is moved to the right, the breaker is in the closed position and the indicator 430 registers on. At the same time, the centering spring 422 draws the shutter 420 to the right covering the opening 402. This prevents the racking crank from being inserted and the breaker from being racked out while in the closed position when it might be in service cr conversely from being racked in, while closed, thereby damaging the separablecontacts 38-3S.

Since many variations and modifications of our invention should now be obvious to those skilled in the art, we prefer to be bound not by the specic disclosure herein contained, but only by the appended claims.

We claim:

l. An arc chute for circuit breakers having-engaging and disengaging contactscom'prising insulation sidewalls, front and back arc runners and a plurality of insulation plates mounted in spaced relation, means for generating a strong magnetic blow-out field for forcing the arc formed on interruption of said contacts into the arc chute, the circuit breaker plates being rectangular in shape at the top and having long tapered lower edges extending from the center of one side of the plate to the lower corner of the opposite side of the plate, and a ceramic spacer interposed between adjacent plates to said supported plate for supporting each plate and spacing said supported plate with respect to said adjacent plates, said ceramic spacer forming with the tapered surface of said supported plates a triangular opening.

2. An arc chute for circuit breakers having engaged and disengaged contacts comprising insulation side walls, iront and back arc runners and a plurality of insulation plates mounted in spaced relation, means for generating a strong magnetic blow-out field for forcing the arc formed on interruption of said contacts into the arc chute, said plates being rectangular in vshape at the top and having long tapered lower edges extending from the center of one side of the plate to the lower corner of the opposite side of the plate, and a ceramic spacer interposed between adjacent plates to said supported plate for supporting each plate and spacing said supported plate with respect tosaid adjacent plates, said ceramic spacer forming with the tapered surface of said supported plates a triangular opening, each of said spacer with its supported plate presenting a decreasing area for the arc as it rises and a narrow slot.

3. An arc chute for circuit breakers having engageable and disengageable contacts comprising insulation side walls, front and back arc runners and a plurality of insulation plates mounted in spaced relation, means for generating a strong magnetic blow-out field for forcing the arc formed on interruption of said contacts into the arc chute, said plates being rectangular in shape at the top and having long tapered lower edges extend- `ing from the center of one side of the plate to the lower corner of the opposite side of the plate, and a ceramic spacer interposed between adjacent plates to said supported plate for supporting each plate and spacing said supported plate with respect to said adjacent plates, said ceramic spacer forming with the tapered surface of said supported plates a triangular opening, said plates being assembled alternately inran interleaved relation and spaced from each other so. that the long tapered surface crosses at the center of the arc chute directly above the path of the arc as it travels up the chute.

4. An arc chute comprising side plates of insulation material, insulating spacers closing the front and rear of said arc chute, an arcing horn mounted on said spacers, said arc chute including a plurality ofv ceramic plates, individual spacers for each of said plates, said plates and spacers forming arcing spaces whichgradually become restricted toward the upper part o said arc chute, the spaces becoming narrow slots and nally closing off substantially half way up said larc chute.

5. An arc chute comprising side plates of insulation material, insulating spacers closing the front and rear of said arc chute, an arcing horn mounted on said spacers, said arc chute including a plurality vof ceramic plates, individual spa-cers rfor each of said plates, said platesv being tapered from one side half way up said arcchute to thel opposite lower cornerof each plate, alternate plates having their tapers extending in opposite directions to form interleaved plates so that said plates and spacers forming arcing spaces gradually become restrictedv toward the upper part of said arc chute, the spaces becoming narrow slots andnally Iclosing off substantially half Way up said arc chute.

6. In a circuit interrupter having a movable contact and a complementary contact, an arc chute comprising side plates of insulation material, insulating spacers closing the front and rear of said arc chute, a front and rear arcing horn, a blow-out coil, said front arcing horn being electrically connected to said blow-out coil at one end of said front arcing horn, said arc chute including a plurality of ceramic plates, individual spacers for said plates, said plates and spacers forming arcing spaces which gradually become restricted toward the upper part of said arc chute, the spaces becommg narrow slots and finally closing off substantially half way up said arc chute, said front arcing horn and blow-out coil being connected in circuit during the opening of the contacts by an arc from said front arcing horn to said movable contact.

7. An arc chute for a circuit interrupter comprising a plurality of parallel spaced insulating plates; each plate having a substantially rectilinear upper end; a transverse surface deiining a recess in a side of each plate substantially centrally of each plate; a longitudinally curved surface connected to said transverse surface and tapering downwardly toward the lower corner of the opposite side of the plate, and insulating spacers located between alternate plates.

8. An arc chute for a circuit interrupter comprising a plurality of parallel spaced insulating plates; each plate having a substantially rectilinear' upper end; a transverse surface dening a recess in a side of each plate substantially centrally of each plate; a longitudinally curved surface connected to said transverse surface and tapering downwardly toward the lower corner of the opposite side of the plate, and insulating spacers located between alternate plates, an additional recess in each plate between each set of alternate plates supported on said insulating spacer.

9. An arc chute comprising at least a rstfsecond and third arc chute plate, each or said plates having a substantially. rectangular `upper section and having a shoulder at the lower end o the section extending in from one edge of .the.p1ate, said plate being tapered from saidshoulder to the other edge at its lowerrnostend, the second plate having its tapered edge extending in the opposite direction from that of the first plate and vthe third plate having its .tapered edge extending in the opposite direction from that-of the` second plate, a removable spacer member interposed between alternate plates, the upper end of said spacer having a slot, the shoulder of itsassociated plate being seated in said slot so that adjacent plates are spacedfromeachrother by the position of said spacer on each side otsaidl slot and insulating plates extending transversely of said plates, one at eachof lthe-opposite edgesfof said plates for closing said plates along .their upper rectangular section.

10. An arc chute comprisingatleasta nrst, second and third arcchuteaplate, each o--said plates having a substantially` rectangular Aupper section and having a shouldei1 .at theA lower end of the section extending .infromH-one edge of the plate, said plate beingtaperedifrom said shoulder to the other edge Yat .its lowermost end, the second plate havingits taperededge extending in the opposite directionfromr-that of ,the irst plate and the third plate having its tapered edge extending in the.opposite...direction from that of the second plate, and a removable spacer member interposed between alternate platesthe upper end of said spacer having a slot, .the shoulder of its associated plate being seated in said slot so that adjacent plates vareuspaced from-each other by the position of. saidspaceroneachrside of said slot.

n: ou

11. An arc chute comprising at least a rst, second and third arc chute plate, each of said plates having a substantially rectangular upper section and having a shoulder at the lower end of the section extending in from one edge of the plate, said plate being tapered from said shoulder to the other edge at its lowermost end, the second plate having its tapered edge extending in the opposite direction from that of the rst plate and the third plate having its tapered edge extending in the opposite direction from that of the second plate, a removable spacer member interposed between alternate plates, the upper end of said spacer having a slot, the shoulder of its associated plate being seated in said slot so that adjacent plates are spaced from each other by the position of said spacer on each side of said slot and insulating plates extending transversely of said plates, one at each of the opposite edges of said plates for closing said plates along their upper rectangular section.

12. An arc chute comprising at least a first, second and third arc chute plate, each of said plates having a substantially rectangular upper section and having a shoulder at the lower end of the section extending in from one edge of the plate, said plate being tapered from said shoulder to the other edge at its lowermost end, the second plate having its tapered edge extending in the opposite direction from that of the rst plate and the third plate having its tapered edge extending in the opposite direction from that of the second plate, and a spacer member interposed between alternate plates, the upper end of said spacci' having a slot, the shoulder of its associated plate being seated in said slot so that adjacent plates are spaced from each other by the position of said spacer on each side of said slot.

JOSEPH D. WOOD. ARTHUR S. CASWELL.

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